In many installations and particularly in fast food restaurants the grills, ovens and the like give off a considerable amount of waste heat which is customarily exhausted to a place of disposal. Attempts to recover this waste heat are complicated by the fact that the gases carry a large amount of grease, entrapped solid wastes and similar solid and precipitable contaminants. Therefore, the exhaust hot gas tends to clog filters, fans, ductwork and heat transfer surfaces. These precipitated and deposited contaminants not only clog up these devices and interfere with proper heat transfer but also require frequent shutdown because in general the disposal system for the gases containing these contaminants must be cleaned every few hours and particularly after peak rush periods such as after the main meal times.
In addition, many restaurants both of the fast food type and the more general type have water scrubbers installed above their exhaust hoods in an attempt to solve this problem of extracting much of the grease and other contaminants before the exhaust gas enters the fan and ductwork system of the exhaust devices. These water scrubbers are very satisfactory and reasonable, but they waste heat values from the exhaust hot gas. For example, when an exhaust gas stream from a grill area which contains considerable heat is subjected to the water spray the temperature of this exhaust gas is frequently reduced by as much as 20.degree. F.
As an example, the exhaust temperatures from electric grills frequently are as much as 90.degree. F., but after passing through the water scrubbers the temperature is reduced to 70.degree. F. In some instances, this difference of 20.degree. is of course wasted heat, as it is not recovered from the scrubbers and therefore the available heat in the resulting scrubbed gases is greatly reduced. From the energy conservation standpoint, it is of course much more desirable to extract waste heat from a 90.degree. F., exhaust rather than a 70.degree. F. exhaust from the water scrubbers.
The heat recovery device of the present invention permits removing the grease and other contaminants by filtering action without materially cooling the exhaust. The filter is easily cleaned. It also provides heat exchangers for recovering the heat with these heat exchangers also being easily cleaned. Furthermore, the device of this invention is versatile in selectively utilizing the air that is heated by recovered waste heat.
One of the features of this invention is to provide a heat recovery device having the above characteristics with the principal features being easy cleanability so that the contaminants can be readily removed as desired.
The invention will be described as related to the embodiment shown in the accompanying drawings.